Final Overall Survival Results from BELLINI, a Phase 3 Study of Venetoclax or Placebo in Combination with Bortezomib and Dexamethasone in Relapsed/Refractory Multiple Myeloma

<jats:title>Abstract</jats:title> <jats:p>Background: Multiple myeloma (MM) is a heterogenous cancer of terminally differentiated plasma cells that typically express elevated levels of antiapoptotic proteins, such as BCL-2. Venetoclax (Ven), a highly selective, potent, oral BCL-2 inhibitor, induces apoptosis in MM cells, and when combined with bortezomib and dexamethasone showed promising efficacy in patients (pts) with relapsed/refractory MM (RRMM; Moreau et al. Blood. 2017;130:2392-2400). The Phase 3 BELLINI study primary analysis showed significantly improved response rates and progression-free survival (PFS) in pts with RRMM treated with Ven added to bortezomib and dexamethasone versus placebo (Pbo); however, increased mortality was observed in the Ven group (Kumar et al. Lancet Oncol. 2020;21:1630-1642). At the initial data cutoff (November 26, 2018), the PFS hazard ratio (HR) was 0.63 (95% CI, 0.44-0.90) and overall survival (OS) HR was 2.03 (95% CI, 1.04-3.95). Pts with t(11;14) translocation or high BCL2 expression showed improved responses and PFS without increased mortality. Here, we present updated safety and efficacy data from the prespecified final OS analysis.</jats:p> <jats:p>Methods: BELLINI (NCT02755597) is a Phase 3, randomized, double-blind, multicenter study of Ven or Pbo combined with bortezomib and dexamethasone in pts with RRMM who had received 1-3 prior lines of therapy and were either sensitive or naïve to proteasome inhibitors. Pts were randomized 2:1 to receive Ven 800 mg/day or Pbo plus bortezomib and dexamethasone. Cycles 1-8 were 21-day cycles with bortezomib 1.3 mg/m 2 on Days 1, 4, 8, and 11 and dexamethasone 20 mg on Days 1, 2, 4, 5, 8, 9, 11, and 12. Cycles 9 and beyond were 35-day cycles with bortezomib 1.3 mg/m 2 on Days 1, 8, 15, and 22 and dexamethasone 20 mg on Days 1, 2, 8, 9, 15, 16, 22, and 23. The primary endpoint was PFS assessed by independent review committee. Key secondary endpoints included overall response rate and OS. BCL2 expression was measured by quantitative polymerase chain reaction with the cutoff for high BCL2 determined using bootstrapping and aggregating thresholds from trees.</jats:p> <jats:p>Results: Of 291 randomized pts (194 to Ven and 97 to Pbo), 33 pts were receiving ongoing treatment (28 with Ven and 5 with Pbo) as of the final OS analysis data cutoff (March 15, 2021). At a median follow-up of 45.6 months, there were 78 (40%) deaths in the Ven arm versus 36 (37%) in the Pbo arm. Updated PFS and OS among all pts and those with t(11;14) or high BCL2 expression are shown in the Table. Among all pts, the median PFS per investigator was 23.4 months in the Ven arm versus 11.4 months in the Pbo arm (HR, 0.58 [95% CI, 0.43-0.78]). In pts with t(11;14), the median PFS was 36.8 months in the Ven arm versus 9.3 months in the Pbo arm (HR, 0.12 [95% CI, 0.03-0.44]). In pts with high BCL2, the median PFS was 30.1 months in the Ven arm versus 9.9 months in the Pbo arm (HR, 0.37 [95% CI, 0.21-0.64]). Median OS was not reached in the Ven or Pbo arm among all pts (HR, 1.19 [95% CI, 0.80-1.77]), pts with t(11;14) (HR, 0.61 [95% CI, 0.16-2.32]), pts with high BCL2 (HR, 0.70 [95% CI, 0.32-1.51]), and pts with t(11;14) or high BCL2 (HR, 0.82 [95% CI, 0.40-1.70]).</jats:p> <jats:p>The most common treatment-emergent adverse events (AEs) with Ven (versus Pbo) were diarrhea (60% versus 50%), nausea (38% versus 23%), and constipation (35% versus 31%). The most common Grade 3/4 AEs (Ven versus Pbo) were thrombocytopenia (16% versus 30%), neutropenia (23% versus 8%), pneumonia (19% versus 13%), anemia (16% versus 15%), and diarrhea (15% versus 11%). Serious AEs occurred in 57% of Ven- and 55% of Pbo-treated pts, with serious infections and infestations occurring in 35% and 29% of pts, respectively. Overall, 26% of pts in the Ven arm and 11% of pts in the Pbo arm experienced an AE leading to Ven or Pbo discontinuation. AEs led to 12 deaths in the Ven arm, with 9 of these deaths due to serious infection; an AE led to 1 death in the Pbo arm. A total of 16 (6%) treatment-emergent deaths occurred (14 [7%] with Ven and 2 [2%] with Pbo), with 3 of these deaths due to disease progression (2 [1%] with Ven and 1 [1%] with Pbo).</jats:p> <jats:p>Conclusion: In the final OS analysis, the addition of Ven to bortezomib and dexamethasone showed significantly improved PFS but resulted in increased mortality versus Pbo in the total population. Consistent with results from previous analyses, Ven added to bortezomib and dexamethasone showed the greatest PFS improvement in pts with t(11;14) or high BCL2, with a favorable benefit-risk profile.</jats:p> <jats:p>Figure 1 Figure 1.</jats:p> <jats:p /> <jats:sec> <jats:title>Disclosures</jats:title> <jats:p>Kumar: Beigene: Consultancy; Celgene: Membership on an entity's Board of Directors or ...